no. 1653. PACIFIC COAST C0PEP0D8— WILSON. 447 



fourth legs. Genital segment rectangular, its margins very straight, 

 and bearing a pair of huge sixth legs at its posterior corners. These 

 arc larger than the anal lamina 1 and much more prominent than in 

 any other known species, and each is armed with three large -pines. 

 The second maxilla- are just showing bifurcate tips, similar to those 

 in the adult male, while the furca has a fat globular base Prom which 

 project a pair of tiny spines, which represent the prongs or rami. 



The mouth-tube is more triangular than in the adult and shows 

 a distinct constriction near the center as in some other specie.-. The 

 other appendages are like those of the adult. 



(insignis, noteworthy or remarkable, in the particulars just given.) 

 This new species is of peculiar interest by reason of its striking 

 coloration and also by the structure of the thorax in both sexes. It 

 furnishes another link in the chain of evidence, and by far the most 

 conclusive of any which has yet appeared, that the genital segment 

 in the Caliginse is really a fusion of two segments, the fifth and sixth 

 of the thorax. Here we not only have the two pairs of legs in both 

 sexes, but the boundaries of the segments are also (dearly indicated 

 by means of grooves. The size of the sixth legs, particularly in 

 young females, is also much greater than that in any other known 

 species or genus of the Caliginse. 



Sul.tamily Tlv'KHIN^. 



TREBIUS TENUIFURCATUS Rathbun. 



Plate LXXII. 



Trebius tenuifurcatus Rathbun, L887, p. 559, pi. xxxix, ti.i, r s. 1 to 3. — Wn> 

 so.n. L907, p. <',7!». |il. w. figs, s to 10. 



Host and record of specimens. — Eight specimens, including both 

 sexes, were obtained from the round sting ray. Urolophus halleri, by 

 Doctor McClendon, at San Diego, California, and are Cat. No. 38600, 

 U.S.N. M. 



F< mult .- -Carapace horseshoe-shaped, one-third wider than long, 

 and, including the third thorax segment, about two-iifths the entire 

 length. Frontal plates less than half the width of the carapace, 

 with a shallow central sinus; lateral lobes wide and bluntly rounded. 

 Transverse grooves, separating the lateral areas situated far back. 

 leaving the thoracic portion shorter than the cephalic as in caudatus. 

 These grooves do not quite reach the lateral margins and there are 

 no notches in the latter, as in other species. 



Eyes huge and well fused on the mid-line about one-third the dis- 

 tance from the anterior margin, dark reddish brown in color. Sec- 

 ond and third thorax segments about the same length, but the third 

 (the first free) segment is considerably the narrower. The sides of 

 this third segment arc strongly inclined toward the central axis. 30 



